1. Field of the Invention
This invention relates generally to electronic devices, and more particularly, to improvement of adhesion of layers therein.
2. Discussion of the Related Art
FIG. 1 illustrates a damascene structure 10 as part of a wafer 12, enlarged for clarity. The structure 10 includes a copper line 14, a silicon nitride layer 16 thereon, and a dielectric layer 18 on the silicon nitride layer 16. The silicon nitride layer 16 and dielectric layer 10 include an opening in which is provided a tantalum liner 20 in contact with the copper line 14. Within the tantalum liner 20 and in contact therewith is another copper line 22, which is in electrical communication with the copper line 14 through the tantalum liner 20.
The resulting structure is then to be capped by depositing a silicon nitride cap layer 24. (FIG. 2) However, it has been found that the interface condition between the copper 22 and silicon nitride cap 24 is such that adhesion between these two parts is poor. In addition, it has been found that silicon from the silicon nitride layer 24 diffuses into the copper line 24, degrading performance thereof.
In an attempt to improve the situation, and again with reference to FIG. 1, a plasma etch is undertaken on the exposed surface of the structure 10 in order to remove native CuO from the surface of the copper 22, with the silicon nitride layer 24 then being deposited thereon. While such a process has been found to improve adhesion between the copper 22 and the silicon nitride 24, further improvement is desired so that a strong bond between the silicon nitride cap 24 and the copper 22 can be achieved.